THE CONTROL OF LONG-TERM CARBON AND NITROGEN DYNAMICS IN CONIFER LOGS BY THE MICROELEMENT MANGANESE This research will test the hypothesis that the long-term carbon and nitrogen dynamics of conifer logs is controlled by the availability of the microelement manganese. Recent research has revealed that a major lignin degradative pathway is controlled by oxidative reactions involving Mn. Prior research has revealed marked differences in the initial Mn concentrations in conifer wood, and these differences correspond to species susceptible to brown-rot (little lignin degraded) versus those susceptible to white-rot (lignin and cellulose breakdown). Since lignin comprises approximately one-third of the original conifer wood, the type of decomposition pathway followed controls the amount of long-term carbon storage. Therefore, this research will have direct implications for understanding the role of coarse woody debris (CWD) in global carbon storage. Harmon, Jarrell and Caldwell hypothesize that: 1) early changes in carbon and nitrogen dynamics are controlled by decomposer colonization patterns, 2) long-term carbon dynamics are controlled by the availability of the microelement Mn which determines, in part, whether lignin is decomposed, and 3) nitrogen dynamics are controlled by the abundance of available carbon and not total carbon. To test these hypotheses the investigators will conduct a three year study of carbon and nitrogen dynamics that examines changes in wood cell wall chemistry, manganese availability, microbial physiology and biochemistry, nitrogen dynamics and mass losses in decomposing logs from different coniferous ecosystems. They will also continue development of a decomposition model that predicts long- term carbon and nitrogen dynamics for many species and sizes of logs. Harmon, Jarrell and Caldwell are innovative and productive investigators of the role of woody debris in forested ecosystems. The are part of the outstanding team of forestry researchers at Oregon State University.
